The then 21-year-old, who had spent the previous season on loan at Goodison Park and was their leading scorer with 16 goals in 33 appearances to help them finish fifth in the Premier League, agreed a five-year contract.
Lukaku played just 15 times in three years at Stamford Bridge, a decisive factor in him choosing to make the move permanent.
"I don't have hard feelings against Chelsea. They gave me the opportunity to come to England and gave me high hopes of playing football," he said.
"I trained with world-class players and worked under world-class managers and without them I wouldn't be here.
"But last year was a very good year and after a short period of time I had the feeling it was the best place to grow as a young footballer.
"I needed to be in the place where it felt right and here I have the confidence of all the technical staff, the trust of the supporters as well and I can grow and develop.
"I have a very good relationship with the players and staff so for me this is the place where I belong."
Lukaku went on to make a further 110 Premier League appearances for Everton, scoring 53 goals, before the Toffees almost trebled their money when he joined Manchester United in 2017.
Lukaku currently plays for Inter Milan, where he has scored 64 goals in 95 appearances.